kasan: add another use-after-free test

Add a new use-after-free test that checks that KASAN detects
use-after-free when another object was allocated in the same slot.

This test is mainly relevant for the tag-based modes, which do not use
quarantine.

Once [1] is resolved, this test can be extended to check that the stack
traces in the report point to the proper kmalloc/kfree calls.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=212203

Link: https://lkml.kernel.org/r/0659cfa15809dd38faa02bc0a59d0b5dbbd81211.1662411800.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 58c1b01..505f77f 100644 (file)
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -612,6 +612,29 @@ again:
        kfree(ptr2);
 }
 
+/*
+ * Check that KASAN detects use-after-free when another object was allocated in
+ * the same slot. Relevant for the tag-based modes, which do not use quarantine.
+ */
+static void kmalloc_uaf3(struct kunit *test)
+{
+       char *ptr1, *ptr2;
+       size_t size = 100;
+
+       /* This test is specifically crafted for tag-based modes. */
+       KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
+
+       ptr1 = kmalloc(size, GFP_KERNEL);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);
+       kfree(ptr1);
+
+       ptr2 = kmalloc(size, GFP_KERNEL);
+       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
+       kfree(ptr2);
+
+       KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr1)[8]);
+}
+
 static void kfree_via_page(struct kunit *test)
 {
        char *ptr;
@@ -1382,6 +1405,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
        KUNIT_CASE(kmalloc_uaf),
        KUNIT_CASE(kmalloc_uaf_memset),
        KUNIT_CASE(kmalloc_uaf2),
+       KUNIT_CASE(kmalloc_uaf3),
        KUNIT_CASE(kfree_via_page),
        KUNIT_CASE(kfree_via_phys),
        KUNIT_CASE(kmem_cache_oob),